The present invention relates to a printer capable of opening a sheet guiding path passing through the printing position of a print head. More particularly, the invention relates to a printer in which a sheet feeding mechanism and a sheet cutting mechanism can be properly provided by devising a mechanism for opening the sheet guiding path.
One type of printer for carrying out printing over a rolled sheet is mounted on a POS (point of sales) terminal. In the related art, there is known a printer for carrying out the printing over a rolled sheet having a structure in which a platen opposed to a print head can also be opened together with a cover for opening a sheet holder formed on a printer body in such a manner that a rolled sheet can be exchanged or loading of the rolled sheet can easily be performed. When the platen is opened together with the cover, a sheet guiding path between the print head and the platen is brought into an open state. Consequently, a sheet drawn out of the loaded rolled sheet is disposed along the print head. Then, when the cover is closed, it is possible to automatically bring a state in which the rolled sheet is interposed between the print head and the platen and is thus drawn out.
For example, Japanese Patent Publication No. 6-79855B (63-98451A) discloses such a rolled sheet printer. In the printer, a platen roller pushed against a thermal head is also attached to the tip of a cover for a sheet holder. In a state in which the cover is closed, the platen roller is protruded toward the thermal head side through an opening portion formed in the sheet holder and is thus pushed against thermal head. When the cover is opened, the platen roller also goes away from the thermal head. Consequently, the lead out portion of the rolled sheet is easily disposed between the platen roller and thermal head. When the cover is then closed, a state in which the rolled sheet is interposed between the thermal head and the platen roller is automatically established.
In the case in which the print head has a dot impact system or an ink jet system, the platen is provided in parallel with the print head while defining a gap therebetween.
In case of a mechanism for opening and closing a platen together with the cover of a sheet holder, it is necessary to carry out a component layout in such a manner that other components are not positioned on the moving loci of the cover and the platen. In the rolled sheet, particularly, an automatic cutting mechanism for cutting a sheet obtained after printing is mounted in many cases. In general, the automatic cutting mechanism is provided on a discharge port of the printed sheet which is formed on the upper face of the printer. In this case, a printing position is placed just below the discharge port, and the cutting mechanism is positioned on the moving locus of the platen defining the printing position. For this reason, it is necessary to devise the moving locus of the platen or the arrangement position and structure of the cutting mechanism.
In the case in which a platen roller is to be pushed against the head face of a thermal head, moreover, it is sufficient that the platen roller is pushed against thermal head in the closure of the cover to move the thermal head backward supported by a spring member. Accordingly, there is no problem even if the moving locus of the platen and a print head cross each other.
In case of a non-contact type print head having the dot impact system or the ink jet system, it is necessary to place the platen in a parallel state in which it is opposed to a head face of the print head while defining a gap therebetween. In this case, it is necessary to constitute the opening mechanism of the platen in such a manner that the moving locus of the platen and the print head do not cross each other.
In case of the print head having the dot impact system, furthermore, it is necessary to attach a ribbon cassette accommodating an ink ribbon to the print head portion. The ribbon cassette is generally attached to establish a state in which the ink ribbon is inserted between the print head and the platen from just above the print head. In the case in which the automatic cutting mechanism of the sheet is provided just above the print head, the automatic cutting mechanism becomes an obstacle so that the ribbon cassette cannot be attached at a touch. For this reason, it is necessary to carry out an operation for once retreating the automatic cutting mechanism together with the cover.